Various fluorinated surfactants are described, for example, in U.S. Pat. Nos. 4,089,804 and 7,741,260, U.S. Patent Application Pub. Nos. 2008/0299487 and 2008/0280230, and V. Huang et al., Proc. of SPIE, Vol. 6519, 65193C-1 (2007).